The excellent lubricating properties of molybdenum disulfide as a dry lubricant as well as in the form of an additive in various oil and grease formulations has resulted in a widespread acceptance and commercial use of this material over a broad range of service conditions. Molybdenum disulfide powders of a so-called lubricant grade comprise finely-particulated high purity powders of an average particle size usually less than 20 microns to as small as a fraction of a micron and which contain less than about 0.5% of contaminating constituents consisting predominantly of silica and other gangue materials present in the ore body from which the molybdenite is derived.
A variety of physical and chemical processing techniques have heretofore been used or proposed for use for effecting a purification of technical grade concentrates of molybdenum disulfide to render the material suitable for use as a lubricant or as a high purity intermediate in synthesizing various molybdenum compounds and metallic molybdenum of corresponding high purity. Typical of such chemical purification processes heretofore proposed are those described in U.S. Pat. Nos. 2,686,156; 3,101,252 and 3,661,508. While the processes as disclosed in the aforementioned patents are effective to produce molybdenum disulfide powders of a desired purity, the processes are generally characterized as being of relatively high cost, relatively complex, requiring a substantial investment in processing equipment and facilities, requiring the use of substantial quantities of high cost chemical reagents, and/or requiring extensive waste treatment facilities for treatment of the waste streams in order that they can be harmlessly discharged into the atmosphere or to waste.
Physical purification techniques such as flotation techniques comprising a plurality of successive grinding, flotation and extraction operations to progressively reduce the quantity of contaminating constituents in the molybdenite concentrate, although costly, have been used for producing molybdenum disulfide powders of the requisite purity.
The process of the present invention overcomes the problems and disadvantages associated with prior art processing techniques by providing a simple, economical and efficient process for reducing silica and other gangue contaminating constituents present in molybdenite concentrates to within commercially acceptable levels. Additionally, the process of the present invention produces a relatively low volume of waste liquid streams which can be simply and effectively treated, whereby they can be harmlessly discharged to waste.